Surge brake with solenoid-actuated master cylinder lock and emergency release

ABSTRACT

A surge-type brake actuator is disclosed which includes a pair of relatively movable members which cooperate with one another to apply the brakes of a towed vehicle when the towed vehicle moves relative to the towing vehicle when the brakes of the latter are applied. The actuator includes a preloaded spring which cooperates with one of the members to urge the latter relative to the other member, and a latching mechanism which normally prevents the spring from generating this relative movement. The latching mechanism is controlled by a solenoid actuator which is wired to the towing vehicle&#39;&#39;s stop light switch so that the latching mechanism is released whenever the operator of the towing vehicle initiates a brake application. A manual control may also be provided in the operator&#39;&#39;s compartment of the towing vehicle so that the solenoid actuator may also be controlled at the discretion of the driver to permit the preloaded spring to apply the towed vehicle&#39;&#39;s brakes a very small amount even if the towing vehicle&#39;&#39;s brakes are released. The latching mechanism includes structure which is responsive to the force generated due to attempted relative movement between the members to permit application of the towed vehicle&#39;&#39;s brakes even when the latching mechanism is engaged when the force generated by attempted relative movement between the vehicles exceeds a predetermined amount.

United States Patent i191 Mizen et al.

[ Oct. 30, 1973 SURGE BRAKE WITH SOLENOID-ACTUATED MASTER CYLINDER LOCKAND EMERGENCY RELEASE [75] Inventors: Walter J. Mizen; Richard L. Lewis;

Richard T. Hendrickson, all of South Bend, Ind.

[73] Assignee: The Bendix Corporation, South Bend, Ind. [22] Filed: June29, 1972 21 Appl. No.: 267,300

[52] U.S. Cl. 188/112 [51] Int. Cl. B60t 7/20 [58] Field of Search 188/3H, 112;

[56] References Cited UNITED STATES PATENTS 3,570,633 3/1971 Gamett188/112 2,229,499 1/1941 Flsette 188/112 Primary Examiner-Duane A. RegerAttorney-Ken C. Decker et al.

57 ABSTRACT A surge-type brake actuator is disclosed which includes apair of relatively movable members which cooperate with one another toapply the brakes of a towed vehicle when the towed vehicle movesrelative to the towing vehicle when the brakes of the latter areapplied. The actuator includes a preloaded spring which cooperates withone of the members to urge the latter relative to the other member, anda latching mechanism which normally prevents the spring from generatingthis relative movement. The latching mechanism is controlled by asolenoid actuator which is wired to the towing vehicles stop lightswitch so that the latching mechanism is released whenever the operatorof the towing vehicle initiates a brake application. A manual controlmay also be provided in the operators compartment of the towing vehicleso that the solenoid actuator may also be controlled at the discretionof the driver to permit the preloaded spring to apply the towed vehiclesbrakes a very small amount even if the towing vehicle's brakes arereleased. The

latching mechanism includes structure which is responsive to the forcegenerated due to attempted relative movement between the members topermit application of the towed vehicles-brakes even when the latchingmechanism is engaged when the force generated by attempted relativemovement between the vehicles exceeds a predetermined amount.

10 Claims, 1 Drawing Figure Lil-til i IIIIIAfEl-l SURGE BRAKE WITHSOLENOID-ACTUATED MASTER CYLINDER LOCK AND EMERGENCY RELEASE BACKGROUNDOF THE INVENTION This invention relates to a surge brake actuator foractuating the brakes of a towed vehicle in response to actuation of thebrakes of the towing vehicle.

As is well known to those skilled in the art, when a vehicle towing atrailer is decelerated, the trailer tends to move toward or overrun thetowing vehicle. Trailer brake actuators which make use of thisoverrunning effect, known as surge-brake actuators, have beencommercially available for many years and have, in general, providedquite satisfactory control of the brakes of the trailer. However, surgebrake actuators also suffer from many deficiencies. For example, sincetrailer brake pressure is created whenever the towed vehicle movestoward the towing vehicle, brake pressure is created when the vehiclecombination is backed up, particularly when the trailer is tracking up aslope. While this deficiency may be overcome by use of less effectivebrakes, this solution is self defeating, since towing a trailer intodays crowded traffic conditions demands more effective, instead ofless effective brakes. Another difficulty with surge trailer brakeactuators is that trailer braking pressure can be created by the surgeactuator while the vehicle combination is coasting down steep hillswhere, in effect, the trailer pushes the towed vehicle. The trailer maythen decelerate momentarily until the hitch forces revert to normaltension. The cycle then repeats itself causing uneven brake wear and insome instances the decelerating influence of the trailer can be felt bythe driver of the towing vehicle. Response time of trailer brakeactuators in the past has been notoriously slow, since the towingvehicle must decelerate before the trailer brakes are applied.Conversely, it is theoretically desirable that the trailer brakes beapplied before the brakes of the towing vehicle are applied to avoidjackknifing. Still another problem encountered in any trailer towingsituation is a condition known as trailer sway, that is, transverserelative movement of the towed vehicle relative to the towing vehicle,as most often occurs during a passing maneuver or when rather windyconditions exist.

SUMMARY OF THE INVENTION Therefore, an important object of our inventionis to provide an improved surge trailer brake actuator which permits thevehicle combination to be backed up without applying the trailersbrakes.

Still another important object of our invention is to prevent generationof braking pressure due to relative movement of the trailer with respectto the towing vehicle while the vehicle combination is coasting down asteep hill.

Still another important object of our invention is to decrease theresponse time required to apply the trailers brakes after the brakes ofthe towing vehicle are applied.

A still further object of our invention is to provide a surge brakeactuator which may be controlled by the vehicle operator in order toinhibit trailer sway.

DESCRIPTION OF THE DRAWINGS The sole FIGURE of the drawings is a view,partly in section, of a surge brake actuator made pursuant to theteachings of our present invention in which the electrical connectionsbetween the actuator and the towing vehicle are illustratedschematically.

DETAILED DESCRIPTION Referring now to the drawings, a surge brakeactuator generally indicated by the numeral 10 includes a structuralnumber 12 which carries a conventional ball and socket type hitch 14which is adapted to couple the member 12 onto a towing vehicle. A secondmember 16 is carried on the towed vehicle or trailer 17 (shown inphantom) and supports a standard automotive master cylinder generallyindicated by the numeral 18. The master cylinder 18 is of thesingle-system type and includes a single piston 20 which is adapted topressurize fluid carried in a reservoir 22 in the conventional mannerwell known to those skilled in the master cylinder art. The outlet portsof the master cylinder 18 are communicated to the trailer brakes (notshown) which are actuated by the fluid pressure developed in the mastercylinder 18. A housing 24 is also connected to the member 16 and isconnected to the member 12 by a pair of links generally indicated by thenumerals 26 and 28, respectively. First pivots 30, 32 connect one end ofthe links 26 and 28, respectively, to the housing 24, and second pivots34, 36 connect the opposite ends of the links 26 and 28, respectively,with the structural member 12. It will therefore be noted that the links26 and 28 which pivotally interconnect the housing 24 and the member 12permit the structural member 16 to move relative to the structuralmember 12 when the trailer or towed vehicle moves relative to the towingvehicle. A shock absorber generally indicated by the numeral 38 isconnected between the members 12 and 16 to dampen road vibrations whichwould otherwise be transmitted through the surge brake mechanism 10.

The master cylinder 18 is actuated by an actuating rod generallyindicated by the numeral 40. The actuating rod 40 is provided with apair of telescoping sections which includes a first section 44 slidablyreceiving a second section 46. A detent cross pin generally indicated bythe numeral 48 is provided on the section 46, and is received within aslot 50 provided in section 44, so that, when the telescoping section 42is fully extended, the engagement of the detents 48 with the end of theslot 50 permits movement of the entire rod 40 with the IhlkS 26 as thelatter pivot about the pivots 30 and 34 in the counterclockwisedirection. First and second spring retainers 52, 54 are carried by thesections 44 and 46 respectively, and spring means generally indicated bythe numeral 56 are disposed between the retainers 52 and 54 andyieldably urge the detent 48 toward the end of the slot 50. Spring means56 also serves to absorb small amounts of the actuating rod 40 so thatthe small movements due to road shock and bumps, etc., will not betransmitted to the master cylinder 18. This, in conjunction with theshock absorber 38, prevents the generation of small braking impulses dueto the aforementioned road shocks and bumps when the vehicle istraversing a relatively rough terrain and the brakes of the vehicle arereleased.

The surge actuator 10 includes a control mechanism generally indicatedby the numeral 58 which includes a housing 60 which extends from thestructural member 16. The housing 60 defines a bore 62 extendingtherethrough which slidably receives a section 44 of the actuating rod40. A sleeve 64 is secured to the rod 40 within the housing60 formovement with the rod 40 and cooperates with the latter to define ashoulder 66 therebetween. A preloaded spring 68 is compressed betweenthe shoulder 66 and another shoulder 70 formed on the wall of thehousing 60. Because the spring 18 is normally compressed when the brakesof both the towed and towing vehicles are released, the spring 68 exertsa force on the actuating rod 40 tending to urge the latter to the right,viewing the FIGURE, to thereby develop a minimum brake actuationpressure in the master cylinder 18. The extent of this movement islimited by the engagement of the detent 48 with the end of slot 50, butis normally sufficiently great to develop a pressure level in the mastercylinder 18 which is sufficient to urge the brake shoes of the trailerbrakes (not shown) into light engagement with the drums. However,movement of the rod 40 relative to the master cylinder 18 due to eitherthe resiliency of the spring 68 or to movement of the trailer toward thetowing vehicle is normally inhibited by a locking mechanism generallyindicated by the numeral 72. Locking mechanism 72 includes reduceddiameter portion 74 on the outer circumferential surface of the sleeve64 which is provided with a sloping ramp surface 76 extending from theportion 74 toward the relatively flat portion of the outercircumferential surface 78 of the sleeve 64. The reduced diameterportion 74 receives spherical force transmitting elements 80. A retainer82' retains the force transmitting elements 80 on the sleeve 64;however, vertical movement of each of the force transmitting elements 80for a distance equal to the depth of the reduced diameter portion 74 ispermitted for a purpose to be described in detail hereinafter. Acup-like retaining structure generally indicated by the numeral 84 isslidably mounted within the housing 60 and is movable from a firstposition illustrated in the drawings in which the sloping inner surface86 of the member 84 is slidably engaged with a portion of the surface ofthe spherical force transmitting elements 80 as illustrated in thedrawing to a second position in which the member 84 is disposed awayfrom the members 80. A spring 88 is provided which urges the structure84 to the first position. As can be seen from the drawings, when theretaining structure 84 is disposed in the first position, the movementof the actuating rod 40 relative to the housing 60 is prevented unlesssufficient force is generated between the rod 40 and housing 60sufficient to urge the spheres 80 up the ramp surfaces 76 and on to thesurface 78 of the sleeve 64. As is evident to those skilled in the art,the force level required to urge the spheres 80 up the ramp surface 76is dependent upon the angle of the ramp surface 76 and also upon theangle of the sloping surface 86 of the retaining structure 84. Since thedesign criteria for locking structures of this type are well known tothose skilled in the art, having been fully disclosed in U. S. Pat. No.3,438,399, owned by the assignee of the present invention andincorporated herein by reference, further details of the lockingstructure will not be described.

The cup-like retaining structure 84 is moved from the first positionillustrated in the drawings to the second position disposed away fromthe force-transmitting elements 80 by an electrical solenoid generallyindicated by the numeral 90. The cup-like structure 84 is mounted on thearmature 92 of the solenoid 90, which is normally spaced at distanceequal to the air gap A from the solenoid core piece 94. Since, as shown,the actuating rod 40 extends through the armature 92 and the core piece94, the actuating rod must be manufactured from a non-magnetic material.The solenoid coil 96 circumscribes the core piece 94 and a portion ofthe armature 92 and is adapted, when an electrical current is passedthrough the coil 96, to move the armature 92 toward the core piece 94,thereby reducing the length of the air gap A. The leads 98 extendingfrom the coil 96 are wired to the vehicles battery 100, and to thevehicles stop light switch 102. Another switch 104, which is wired inparallel to the stop light switch 102, is mounted in a position wherethe switch 104 is easily accessible to the operator of the towingvchicle. Therefore, an electric current will be passed through the coil96 when either the vehicles stop light switch 102 is actuated or whenthe manually actuated switch 104 is actuated.

MODE OF OPERATION The various components of the surge brake actuator 10are illustrated in the drawings in the positions which they assume whenthe brakes of both the towing vehicle and the towed vehicle or trailerare released. In this position, the locking mechanism 72 preventsrelative movement between the actuating rod 40 and the master cylinder18 as described hereinabove. Therefore, substantially no pressure isgenerated in the master cylinder 18 and the brakes of the vehicle remainin the released position. However, when the operator of the towingvehicle initiates a brake application, the stop light switch 102 isclosed immediately so that a current will be passed through the coil 96of the solenoid 90. When this occurs, the cup-shaped structure 84 ismoved to the second position, away from the forcetransmitting elements80, to thereby permit the preloaded spring 68 to urge the actuating rod40 toward the master cylinder 18, thereby generating pressure in thelatter sufficient to urge the brake shoes of the trailer brakes (notshown) into light frictional engagement with the rotating drums thereof.As the towing vehicle continues to decelerate, the trailer will movetoward the towing vehicle, since the force generated by theaforementioned light contact by the shoes against the drum isinsufficient to quickly reduce the speed of the trailer. Upon relativemovement of the trailer with respect to the towing vehicle, the links 26and 28 pivot about the pivots 34 and 36, respectively. Although theactuating rod 40 is attached to the link 26, it moves a substantiallyshorter distance relative to the structural member 12 than does themaster cylinder 18, since the lever arm between the point of attachmentof the rod 40 to the link 26 is much closer to the pivot 34 than is thepivot 30 in which the housing 28, and therefore the structural member 16and master cylinder 18, are attached to the links 26. Therefore,relative movement occurs between the rod 40 and the master cylinder 18,so that the piston 20 of the latter is urged to the right, viewing theFIGURE, thereby increasing the fluid pressure level generated in themaster cylinder. This fluid pressure level, of course, is communicatedto the brakes of the towed vehicle, further actuating the latter. Sincethe extent of relative movement between the trailer and the towingvehicle is dependent upon the deceleration of the latter, the brakingeffect on the trailer brakes will be proportional to this deceleration.Furthermore, since the brakes of the trailer are actuated a small amountimmediately when the stop light switch 102 is actuated, the undesirabletime lag between actuation of the towing vehicles brakes and actuationof the trailer brakes inherent in surge brake mechanisms known to theprior art is reduced in the present design. When the brakes of bothvehicles are released and hitch forces revert to normal, rod 40 is movedto the left viewing the FIGURE, to again compress the spring 68.

Although normally no relative movement between actuating rod 40 andmaster cylinder 18 can occur unless the solenoid 90 is actuated, whenthe force due to attempted relative movement between the member 40 andthe master cylinder 18 is sufficiently great that the spheres 80 areurged up the ramp surfaces 76, such relative movement can occur eventhough the cup-shaped member 84 remains disposed in the first positionas illustrated in the drawings. This feature provides failsafe operationin case a malfunction should occur in the solenoid 90 which wouldprevent any actuation of the brakes of the trailer. Although the forcelevel required to disengage the force-transmitting elements 80 fromtheir recesses 74 must be low enough to protect the vehicles againstdamage, it must be high enough so that the normal movement of thetrailer with respect to the towing vehicle, such as occurs when thevehicle combination is traveling down a steep grade or when the vehiclecombination is backed up, the sphere 80 will remain on the portion 74 sothat the locking mechanism 72 prevents any actuation of thetrailersbrakes.

The switch 104 is optionally provided so that the vehicle operator mayindependently actuate the solenoid 90 to permit the spring 68 togenerate a small braking force in the trailer brakes even when thebrakes of the towing vehicle are released. This is particularlydesirable in case the brakes of the towing vehicle should fail so that aminimum level of braking will be available, although this minimum levelwill be small. Manual control of the solenoid 90 by the switch 104 isalso desirable to inhibit trailer sway or relative lateral trailermovement with respect to the towing vehicle. When trailer sway occurs,the vehicle operator may briefly actuate the trailers brakes by usingthe switch 104 even when the brakes of the towing vehicle are releasedentirely, thereby retarding and correcting trailer sway.

We claim:

1. In a brake control device for actuating the brakes of a towed vehiclein response to actuation of the brakes of a towing vehicle:

brake-applying means responsive to relative movement between saidvehicles to apply the brakes of the towed vehicle upon movement of saidtowed vehicle toward said towing vehicle; and

control means normally inhibiting said brakeapplying means to preventactuation of the brakes of the towed vehicle, said control means beingreleasable upon initiation of a brake application by the operator of thetowing vehicle to permit actuation of the brakes of the towed vehicle;

said control means including locking means normally preventing actuationof said brake-applying means said actuator being actuated by initiationof a brake application of the towing vehicle whereby actuation of thebrakes of the towing vehicle permits said energy storage device to applythe brakes of the towed vehicle to a first predetermined level even inthe absence of relative movement between the towed vehicle and thetowing vehicle. and subsequent relative movement between the towingvehicle and the towed vehicle actuates the brakes of the latter by anadditional amount.

2. The invention of claim 1; and

means actuated by the operator of the towing vehicle to operate saidactuator whereby the brakes of the towed vehicle may be actuated whenthe brakes of the towing vehicle are released.

3. In a brake control device for actuating the brakes of a towed vehiclein response to actuation of the brakes of a towing vehicle;

brake-applying means responsive to relative movement between saidvehicle to apply the brakes of the towed vehicle upon movement of saidtowed vehicle toward said towing vehicle; and

control means normally inhibiting said brakeapplying means to preventactuation of the brakes of the towed vehicle, said control means beingreleasable upon initiation of a brake application by the operator of thetowing vehicle to permit actuation of the brakes of the towed vehicle;

said brake-applying means including a pair of relatively movablemembers, said members moving relative to one another upon relativemovement between the vehicles to apply the brakes of said towed vehicle;

said control means including locking means normally preventing relativemovement between said members, and actuating means actuatable inresponse to initiation of a brake application of the towing vehicle torelease said locking means to permit relative movement between saidmembers.

4. The invention of claim 3;

one of said relatively movable members including a fluid pressuregenerating device communicated to the brakes of the towed vehicle.

5. The invention of claim 3; and

an energy storage device operably connected to one of said members forapplying the brakes of the towed vehicle upon actuation of saidactuating means to release said locking means.

6. The invention of claim 5:

said locking means releasing to permit relative movement between saidmembers in the absence of actuation of said actuating means when theforce generated by attempted relative movement between said membersexceeds a predetermined amount.

7. The invention of claim 5:

said energy storage means having a preload of predetermined magnitudeyieldably urging said members relative to one another, said lockingmeans normally preventing relative movement between said members clue tothe preload of said energy storage means; and

means operable by the operator of the towing vehicle to actuate saidactuating means to release said locking means to permit the preload ofsaid energy storage means to actuate the brakes of the towed vehicle.

8. The invention of claim 5:

said energy storage means having a preload of predetermined magnitudeyieldably urging siad members relative to one another, said lockingmeans normal ly preventing relative movement between said members due tothe preload of said energy storage means, whereby the brakes of thetowed vehicle are applied by an amount governed by the preload of theenergy storage means immediately upon initiation of a brake applicationof the towing vehicle and before the towing vehicle has deceleratedsufficiently to permit the towed vehicle to move relative to the towingvehicle.

9. The invention of claim 6:

said locking means including a recess carried by one of said members, aforce transmitting member disposed in said recess, and structure carriedwith the said energy storage device being a preloaded spring.

1. In a brake control device for actuating the brakes of a towed vehicle in response to actuation of the brakes of a towing vehicle: brake-applying means responsive to relative movement between said vehicles to apply the brakes of the towed vehicle upon movement of said towed vehicle toward said towing vehicle; and control means normally inhibiting said brake-applying means to prevent actuation of the brakes of the towed vehicle, said control means being releasable upon initiation of a brake application by the operator of the towing vehicle to permit actuation of the brakes of the towed vehicle; said control means including locking means normally preventing actuation of said brake-applying means and an actuator for releasing said locking means; and an energy storage device connected to said brake-applying means for operating the latter upon release of the locking means; said actuator being actuated by initiation of a brake application of the towing vehicle whereby actuation of the brakes of the towing vehicle permits said energy storage device to apply the brakes of the towed vehicle to a first predetermined level even in the absence of relative movement between the towed vehicle and the towing vehicle, and subsequent relative movement between the towing vehicle and the towed vehicle actuates the brakes of the latter by an additional amount.
 2. The invention of claim 1; and means actuated by the operator of the towing vehicle to operate said actuator whereby the brakes of the towed vehicle may be actuated when the brakes of the towing vehicle are released.
 3. In a brake control device for actuating the brakes of a towed vehicle in response to actuation of the brakes of a towing vehicle; brake-applying means responsive to relative movement between said vehicle to apply the brakes of the towed vehicle upon movement of said towed vehiCle toward said towing vehicle; and control means normally inhibiting said brake-applying means to prevent actuation of the brakes of the towed vehicle, said control means being releasable upon initiation of a brake application by the operator of the towing vehicle to permit actuation of the brakes of the towed vehicle; said brake-applying means including a pair of relatively movable members, said members moving relative to one another upon relative movement between the vehicles to apply the brakes of said towed vehicle; said control means including locking means normally preventing relative movement between said members, and actuating means actuatable in response to initiation of a brake application of the towing vehicle to release said locking means to permit relative movement between said members.
 4. The invention of claim 3; one of said relatively movable members including a fluid pressure generating device communicated to the brakes of the towed vehicle.
 5. The invention of claim 3; and an energy storage device operably connected to one of said members for applying the brakes of the towed vehicle upon actuation of said actuating means to release said locking means.
 6. The invention of claim 5: said locking means releasing to permit relative movement between said members in the absence of actuation of said actuating means when the force generated by attempted relative movement between said members exceeds a predetermined amount.
 7. The invention of claim 5: said energy storage means having a preload of predetermined magnitude yieldably urging said members relative to one another, said locking means normally preventing relative movement between said members due to the preload of said energy storage means; and means operable by the operator of the towing vehicle to actuate said actuating means to release said locking means to permit the preload of said energy storage means to actuate the brakes of the towed vehicle.
 8. The invention of claim 5: said energy storage means having a preload of predetermined magnitude yieldably urging siad members relative to one another, said locking means normally preventing relative movement between said members due to the preload of said energy storage means, whereby the brakes of the towed vehicle are applied by an amount governed by the preload of the energy storage means immediately upon initiation of a brake application of the towing vehicle and before the towing vehicle has decelerated sufficiently to permit the towed vehicle to move relative to the towing vehicle.
 9. The invention of claim 6: said locking means including a recess carried by one of said members, a force transmitting member disposed in said recess, and structure carried with the other member and movable in response to actuation of said actuating means from a first position in which said structure engages said force transmitting element to thereby lock said one member against movement relative to the other member to a second position disengaged from said force transmitting member to permit relative movement between said members; said force transmitting element being urged out of said recess to permit relative movement between said members when the force generated by attempted relative movement between said members exceeds a predetermined level.
 10. The invention of claim 1: said energy storage device being a preloaded spring. 